We have a 22k gallon IG gunite pool with a mineral springs SWC. This is the 2nd year of operation. We opened 2 weeks ago and everything went well, except some of the stains we accumulated over the winter didn't go away. I assumed they were from leaves b/c they were mostly on the steps and love seat, but now there is some discoloration to the bottom and the face of the steps. The darkest spots are brown and are about the size of a one dollar coin, but the spreading is more of a light brown coating spreading around the stains.

I tried Ph down crystals on one or two, figuring that was the same as concentrated muriatic acid, but it didn't work. I also tried directly placing a little shock on the spot and it seemed to lighted over a few days but didn't work entirely and I don't need/want that much chlorine in the pool all the time.

This a.m. I tried crushed Vitamin C tablets directly on the stains and it worked, so based on what I've read here it would seem to be a metal problem. (not sure where the metal would have come from b/c I had no probs last year and the fill water this year was 95% rain/snow from the winter and 5% hose water, which is what I used for about 20% of the water last year, but how it got here isn't really the issue.

Readings are:

FC = 12
TC = 12 (is that possible/correct? I took it twice so I think it is accurate, but that doesn't seem good)
Ph 7.2
Alk = 100 (earlier this week I added 4 lbs baking soda b/c alk had been too low)
CYA = 70
Temp = 72

I added 200 lbs salt last week as the mineral reading on the SWC was 1300. That reading is now at 3000, but I've turned it off due to the high clorine rating.


So, what do I do about the stains, and am I correct that the chlorine it way too high?

Thanks